An image reading device is known in which a medium is carried and the image formed on the carried medium is read. In a printer meant for printing on a carried medium; a mechanism is installed by which, when the medium passes obliquely, the obliqueness is corrected (see Japanese Laid-open Patent Publication No. 4-49148, Japanese Laid-open Patent Publication No. 7-89643 and Japanese Laid-open Patent Publication No. 9-86726).
In an image reading device, mediums of various sizes are carried unlike in a printer. Hence, there are times when it is difficult to properly correct the obliqueness of a medium.